Retirement Plans Retirement Plans (Reconciliation of Change In Value For Level 3 Assets) (Details) - Fair Value, Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Level 3, beginning	$ 451	$ 405
Gains (Losses) on assets held	1	49
Gains (Losses) on assets sold	37	(28)
Purchases, sales and settlements, net	(18)	25
Level 3, ending	$ 471	$ 451

Fair value measurement with unobservable inputs reconciliation recurring basis asset gains losses on assets held.

No definition available.

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- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset gains losses on assets sold.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Period Type:	instant

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